1. Field of the Invention
This invention relates in general to an offset window detector, and more particularly to an offset window detector that determines whether a summation of input signals falls within a window.
2. Description of Related Art
Today""s wireless communications markets are being driven by a multitude of user benefits. Products such as cellular phones, cordless phones, pagers, and the like have freed corporate and individual users from their desks and homes and are driving the demand for additional equipment and systems to increase their utility. As a result digital radio personal communications devices will play an increasingly important role in the overall communications infrastructure in the next decade.
Mixed-signal integration and power management have taken on added importance now that analog and mixed analog-digital ICs have become the fastest-growing segment of the semiconductor industry. Integration strategies for multimedia consoles, cellular telephones and battery-powered portables are being developed, as well as applications for less integrated but highly specialized building blocks that serve multiple markets. These building blocks include data converters, comparators, demodulators, filters, amplifiers and voltage regulators.
One important aspect of digital radio personal communications devices is the integration of the RF sections of transceivers. Compared to other types of integrated circuits, the level of integration in the RF sections of transceivers is still relatively low. Considerations of power dissipation, low offset budgets, form factor, and cost dictate that the RF/IF portions of these devices evolve to higher levels of integration than is true at present. Nevertheless, there are some key barriers to realizing these higher levels of integration.
For example, most applications provide a comparator circuit in an RF receiver system to compare different signals. For offset window detectors, input signals are compared to a reference voltage and a resulting signal is used to control an offset integrator. The offset window detector with hysteresis is used to detect when the offset in a circuit has settled out and to direct the integrators to hold their acquired offset. However, the information received from the offset window detector controls the integrators to maintain a voltage level predetermined in a hysteresis window. Therefore, the offset window detector determines parameters such as: signal level budget, minimum gain step size, amplifier voltage limits, speed of input level variations due to multi-path fading and demodulator dynamic range. Input signal level regulation is critical for these components. To provide this regulation, the window detector implements circuitry which compares an signal to the reference voltage. A reference voltage source generates a reference voltage window that is used to determine if a resulting input signal is less than, greater than, or equal to the reference voltage.
It can be seen then that there is a need for an offset window detector to determine whether the summation of input signals falls within a window.
It can also be seen that there is a need for an offset window detector that senses input signals and drives digital circuits in response thereto to produce the desired gain and to attenuate the offset voltages.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an offset window detector circuit that determines whether a summation of input signals falls within a window.
The present invention solves the above-described problems by providing an offset window detector that determines whether the summation of input signals falls within a window and drives digital circuits in response thereto to produce the desired gain and to attenuate the offset voltages.
A system in accordance with the principles of the present invention includes comparing an input signal to a first reference voltage to produce a first output signal and comparing the input signal to a second reference voltage to produce a second output signal, wherein the first and the second output signal indicates whether the input signal is within a reference window defined by the first and the second reference voltages.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention further includes summing the value of the input signal.
Another aspect of the present invention is that the summing of the value of input signal further includes summing a maximum input signal value with a minimum input signal value resulting in a cumulative input signal value.
Another aspect of the present invention is that the summing of the value of input signal further includes summing an in-phase minimum signal with an in-phase maximum signal and a quadrature minimum signal with a quadrature maximum signal.
Another aspect of the present invention is that the summing of the value of input signal further includes sampling the input signal.
Another aspect of the present invention is that the input signal further includes computing an addition and a subtraction of the input minimum signal with the input maximum signal to determine a polarity of a resulting signal.
Another aspect of the present invention is that the subtraction of the input minimum signal with the input maximum signal further includes reversing the polarity of the positive and negative components of the input signal.
Another aspect of the present invention is that the computing of the addition and the subtraction further includes sampling the input signal via a parasitic insensitive sampling network.
Another aspect of the present invention is that the parasitic insensitive sampling further includes accomplishing the addition and the subtraction by a charge sharing of parallel capacitors.
Another aspect of the present invention is that the sampling of the input signal further includes preamplifying a low level signal.
Another aspect of the present invention is that the sampling of the input signal further includes latching a voltage level.
Another aspect of the present invention is that the sampling of the input signal further includes generating two nominally identical voltages to reduce cross talk between a first preamplifier signal and a second preamplifier signal.
Another aspect of the present invention is that the method further includes providing a reference voltage.
Another aspect of the present invention is that the providing of the reference voltage further includes generating all needed reference voltages from a single source.
Another aspect of the present invention is that the reference voltage further includes providing a control signal to regulate the reference voltage wherein the control signal varies a hysteresis window.
Another aspect of the present invention is that the offset window detector further includes an architecture which utilizes a minimal number of circuits to perform the detection function.
Another aspect of the present invention is that the offset window detector further includes producing the output to drive digital circuitry to achieve the desired gain and the attenuation of offset voltages.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.